Extra large CDMA antenna

Submitted: Monday, Apr 11, 2005 at 23:47
ThreadID: 21983 Views:3362 Replies:6 FollowUps:2
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Howdy, I bought a new Nokia 6225 CDMA phone with a genuine Nokia car kit (only $49 extra from Telstra at the moment) and I'm a bit bewildered at the options available for external CDMA antenna's. I've had a good poke around the archives and saw a lot of RFI 1795 fans, but not much mentioned about the big ones.

A 2.1m one was recommended as the best by a reputable company, but will set me back about $220 with base. This may be just too high for practical application so does extra height and price really make a significant difference?

Can anyone recommend a particular model? Any good people to see in Perth for price/advice on said item?

Cheers
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Reply By: Mike Harding - Tuesday, Apr 12, 2005 at 08:14

Tuesday, Apr 12, 2005 at 08:14
A 7 foot high antenna is a _big_ antenna to put on a vehicle. A number of amateur radio operators run antennas this size but especially during 4WDing there is a significant chance of breaking something.

Look at the dB (decibel) gain figure for each antenna this is a partial measure of it's efficiency - an increase of 3dB equates to a doubling of the signal which _does not_ equate to a doubling of the distance you can operate over. In real conditions an extra 3dB may make little difference - otoh it may mean you can _just_ make a call when otherwise you would not be able too. I guess "you pays your money and takes your chance"? Personally I wouldn't pay $220 for a CDMA antenna or want a 7 foot pole hanging off the vehicle.

Mike Harding
AnswerID: 106304

Follow Up By: V8Diesel - Tuesday, Apr 12, 2005 at 08:36

Tuesday, Apr 12, 2005 at 08:36
Mike, my thoughts too. It is as big as my HF antenna which is PITA, but as I don't know anything about them it's whether they are worth the hassle for the extra dB gain.

Any particular make/model recommendations of more practical ones?

Cheers
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FollowupID: 363314

Follow Up By: Mike Harding - Tuesday, Apr 12, 2005 at 10:05

Tuesday, Apr 12, 2005 at 10:05
Hi V8Diesel

Antennas are always a difficult thing to speak on in a general manner because the whole propagation and power transfer process is so damn complex that what might work well in my circumstances may not for you and, I hasten to add, I am no expert on RF systems.

In my experience (at HF) a wire antenna in the trees will usually do better than a vehicle mounted whip but is a lot harder to put up – especially if you’re on the move! :). The only other thing I can think of is to buy an antenna from these guys

http://www.qsl.net/vk3frc/club_projects.htm

it's still about 7 feet tall but has a threaded base which means you could remove and attach it very easily. And, for a vertical, these seem to be _very_ good antennas both from my own experience of talking to people using them and from all the 2nd hand reports I've heard. I think they cost around $100 or so plus a base, if you need one. And because they are made and sold by an Amateur radio club it’s not really a commercial thing from the pricing perspective.

btw these antennas will _only_ work on the HF frequencies they would be useless for CDMA/GSM mobile phones.

Mike Harding

mike_harding@fastmail.fm
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FollowupID: 363330

Reply By: Rod W - Tuesday, Apr 12, 2005 at 13:17

Tuesday, Apr 12, 2005 at 13:17
I went to WACB. On his recommendation I bought a 6bd antenna, he reckoned it is 40 times better that phone antenna. It’s about 800mm long, cost was about $170. Mounted it on a SS bracket ($37) from ARB.
AnswerID: 106344

Reply By: Member - Jeff M (WA) - Tuesday, Apr 12, 2005 at 14:54

Tuesday, Apr 12, 2005 at 14:54
I picked up a 6db with spring base (about 1m or so) from Dicksmith of all places, $130.
Works really well and it's not even located very well height wise as it's mounted to the low nudge bar on the surf. We very rarley drop out while out bush, only in really hilly terrain when your down the bottom or if we really go out of the way. On most highways we have coverage all the time.
AnswerID: 106359

Reply By: BenSpoon - Tuesday, Apr 12, 2005 at 15:51

Tuesday, Apr 12, 2005 at 15:51
Im in the process now of removing a 2.1m aerial we have strapped to the side of a donger for CDMA fax/phone comms. I first started with a 900mm Scalar 6db and that barely held the signal, the 2.1m was no significant increase. I have had to go to a directional aerial now (painful.)
If someone does find something out of sight for CDMA, do share. Also, does anyone know what the rule is for determining the length of the wire to add on to the aerial base? Im keen to see if I can do anything to help the signal im getting.
AnswerID: 106369

Reply By: craig - Tuesday, Apr 12, 2005 at 23:39

Tuesday, Apr 12, 2005 at 23:39
Have a look at Mobile One Tri-band CN8918S, 5db, 1100mm, and has a locking grub screw on the base.
AnswerID: 106463

Reply By: Member - Captain (WA) - Thursday, Apr 14, 2005 at 06:19

Thursday, Apr 14, 2005 at 06:19
Hi V8Diesel,

I too have the Nokia 6225 with full car kit and RFI 1795 antenae (approx 800mm long). On my UHF, I run a 2.1m aerial when out of town and have noticed a significant improvement in range. My UHF experience has shown the taller the antenae, the better the range (and noticeably better, not just a minor improvement).

But to translate that to CDMA experience is not straightforward. Due to their nature, CDMA has a finite distance (approx 100kms from a base station), unlike UHF. So while the bigger CDMA antenae cannot extend the range greater than 100kms, within the 100 km boundary it will give better chance of reception depending on terrain. This is purely due to the extra height to get your signal higher up. You would be just as well off putting a standard CDMA antenae on an extension pole!!!

Personally, I would stick with the RFI 1795 for the CDMA, but I do like my 2.1m UHF when out of town (gotta watch those tree covered tracks though!).

Cheers

Captain

PS. Currently in London at the moment, haven't seen a single car phone antenae here at all, range does not seem to be a problem! Everyone seems to run bluetooth ear pieces here.
AnswerID: 106641

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